B. when heat energy is absorbed by matter, the matter's temperature increases.
when heat energy is released by matter, the matter's temperature decreases. the matter can also change from one phase to another when heat energy is absorbed
or released. identify whether matter absorbs heat or releases heat as each of the following phase changes occur.
i. from solid to liquid (melting)
ii. from liquid to solid (freezing or hardening)
iii. from liquid to gas (evaporation)
iv. from gas to liquid (condensation)

Explanation:

i. From solid to liquid (melting)

For melting to occur, heat must be absorbed by the substance being melted. When the substance gains significant amount of heat, its particles begins to vibrate and move on top of one another.

ii. From liquid to solid (freezing or hardening)

In this phase change, heat is removed from the system. This allows for the molecules to lose their kinetic energies and form an ordered arrangement from their liquid or molten state.

iii. From liquid to gas (evaporation)

As randomness continues to increase, more heat is absorbed to break the attractive forces between molecules of liquids. Phase change from liquid to gas is a heat absorbing process.

iv. From gas to liquid (condensation)

In condensation, heat is lost by a substance. To condense or collect gas particles together, heat must be removed from the system. This allows for a diminished kinetic energy among the particles of the system.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.